1/** 2 * @fileoverview Rule to disallow a duplicate case label. 3 * @author Dieter Oberkofler 4 * @author Burak Yigit Kaya 5 */ 6 7"use strict"; 8 9//------------------------------------------------------------------------------ 10// Requirements 11//------------------------------------------------------------------------------ 12 13const astUtils = require("./utils/ast-utils"); 14 15//------------------------------------------------------------------------------ 16// Rule Definition 17//------------------------------------------------------------------------------ 18 19module.exports = { 20 meta: { 21 type: "problem", 22 23 docs: { 24 description: "disallow duplicate case labels", 25 category: "Possible Errors", 26 recommended: true, 27 url: "https://eslint.org/docs/rules/no-duplicate-case" 28 }, 29 30 schema: [], 31 32 messages: { 33 unexpected: "Duplicate case label." 34 } 35 }, 36 37 create(context) { 38 const sourceCode = context.getSourceCode(); 39 40 /** 41 * Determines whether the two given nodes are considered to be equal. 42 * @param {ASTNode} a First node. 43 * @param {ASTNode} b Second node. 44 * @returns {boolean} `true` if the nodes are considered to be equal. 45 */ 46 function equal(a, b) { 47 if (a.type !== b.type) { 48 return false; 49 } 50 51 return astUtils.equalTokens(a, b, sourceCode); 52 } 53 return { 54 SwitchStatement(node) { 55 const previousTests = []; 56 57 for (const switchCase of node.cases) { 58 if (switchCase.test) { 59 const test = switchCase.test; 60 61 if (previousTests.some(previousTest => equal(previousTest, test))) { 62 context.report({ node: switchCase, messageId: "unexpected" }); 63 } else { 64 previousTests.push(test); 65 } 66 } 67 } 68 } 69 }; 70 } 71}; 72